The present invention relates to a grass trimmer and, more particularly, to a structure of a grass trimmer that allows a cutting blade to be correctly mounted in coaxial relationship with an output shaft in a cutting blade mounting head portion of the grass trimmer.
A grass trimmer has a cutting blade mounting head portion located at, for example, the forward end of an elongated operation column. A cutting blade, such as a disc saw blade, is dismountably mounted, through a cutting blade mounting member, to the output shaft in the cutting blade mounting head portion, so that the cutting blade is driven and rotated by the power from a prime mover, such as an internal combustion engine, at the rearward end of the operation column. During operation, the cutting blade and the cutting blade mounting member are rotated at a high speed. Therefore, it is necessary that, in order to prevent generation of abnormal vibration during operation, the blade and the blade mounting member be mounted to the output shaft while they are correctly centered with respect to the output shaft. For this purpose, it has been necessary that the fitting portion such as a spline portion, at which the output shaft and the cutting blade mounting member are fitted together in such a manner as to prevent them from rotating relative to each other, be formed by a cutting process performed with a high level of precision. This machining necessitates a very high processing cost, and thus involves a disadvantage.